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For the three astrophysicists who won the Nobel Prize in physics
today (Oct. 4), it was only a matter of when, not if, they would
get the prize, their peers said. Their discovery that the
universe's expansion is accelerating was an Earth-shattering
revelation that led to the bizarre concept of dark energy.

For such a monumental find, experts said, the Nobel was
inevitable.

"We expected it from the day the research paper was published
back in the1990s,"astrophysicist Neil deGrasse Tyson, director of
the Hayden Planetarium at the American Museum of Natural History,
told SPACE.com. "The fact that there's a committee in Sweden who
agrees with what we've known all along is not a surprise to us in
the astrophysics community. It is a discovery that's bigger than
the prize itself."

The Nobel Prize committee announced the decision today to
award 2011's prize to Saul Perlmutter of the Lawrence
Berkeley National Laboratory and the University of California,
Berkeley; Brian Schmidt of the Australian National University;
and Adam Riess of Johns Hopkins University and the Space
Telescope Science Institute.

Perlmutter headed up one team, and Schmidt and Riess another.
They independently found that the ballooning of the universe over
time is speeding up, contrary to all expectations.
[ 7
Surprising Things About the Universe ]

Scientists were left scratching their heads regarding the cause
of this speeding up of the universe's expansion, which wouldn't
be possible unless there was a force working against the inward
pull of gravity. This force they have named " dark
energy."

"All we can say is that there's an entity that is forcing the
universe to accelerate outside of the wishes of gravity," Tyson
said. "The term 'dark energy' seems apt, but we don’t know what
it is — that remains a mystery. The Nobel is for the discovery of
this mystery."

The researchers, in fact, had set out to find the opposite: to
measure just how much the
expansion of the universe was decelerating, as it was
expected to do because of gravity.

"They wanted to know to what extent gravity is slowing down the
expansion of the universe — and their rivalry to 'get there
first' was fierce," said journalist Richard Panek, who wrote a
book about the discovery called "The 4% Universe: Dark Matter,
Dark Energy, and the Race to Discover the Rest of Reality"
(Houghton Mifflin Harcourt, 2011). "What they discovered
instead is that the universe is doing the opposite of what they
expected — that the expansion is speeding up under the influence
of some force that, on the cosmic scale, is overpowering gravity.
Scientists want to catch the universe doing something weird, and
they caught it doing the weirdest thing of all."

The mind-bending measurement, made by studying faraway star
explosions called Type 1a supernovas that allowed the researchers
to precisely measure cosmic distances, shook all of science.

"It was revolutionary for physics and cosmology," said John
Carlstrom,director of the Kavli Institute for Cosmological
Physics at the University of Chicago."The acceleration and that
there is some sort of dark energy is now widely accepted by
experts in the field. Now if only we could understand what the
dark energy really is! That is one of the biggest mysteries in
all of physics."

Other experts agreed that the dark energy revealed by Perlmutter,
Schmidt and Riess will play a defining role in scientists' quest
to understand the universe going forward. [ What is Dark
Energy? ]

"Arguably understanding the nature of dark energy is the biggest
challenge that physics is facing today," said Mario Livio, a
colleague of Riess' at the Space Telescope Science Institute.
"While dark energy has not played a huge role in the evolution of
the universe in the past, it will play the dominant role in the
evolution in the future. The fate of the universe depends on the
nature of dark energy. I am clearly very excited about Adam,
Saul, and Brian winning the prize."

And the significance of the discovery extends even beyond the
fate of our universe, to the question of whether there are in
fact
multiple universes, with different amounts of dark energy in
each.

"The discovery was amazing," said Harvard University theoretical
physicist Lisa Randall, author of the new book "Knocking on
Heaven's Door: How Physics and Scientific Thinking Illuminate the
Universe and the Modern World" (Ecco, 2011). "For many, it
changed their research agenda. I speak especially of those who
work on the 'landscape' of multiple universes and the 'anthropic
principle' that says we can live only in a universe with such
small dark energy."

You can follow SPACE.com senior writer Clara Moskowitz on
Twitter @ ClaraMoskowitz. Follow
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